Methodologies for testing wafers during the manufacturing process is becoming increasingly important as devices are produced in smaller and more tight wafer configurations. Usually, destructive cross-sections of wafers are obtained to assess the quality of the wafer. However, this is a destructive process, and as a result, only a small number of wafers are selected for testing. In some instances, electrical tests at the end of the wafer determine if any deficiencies exist by accessing the quality of the semiconductor device formed on the wafer. Even if defects are detected, however, these defects were not detected until the end of wafer processing. As a result, those problems in the manufacturing process or with the equipment used during the manufacturing may not be detected and numerous defective wafers may be produced before problems with the manufacturing processes are detected.
Scanning electron microscopes (SEM) and similar line width metrology tools have been successfully used in semiconductor manufacturing processes. However, it is often difficult for an operator to detect errors by simply viewing the waveform from a scanning electron microscope.
In commonly assigned and copending patent application serial number 08/957,122, filed Oct. 24, 1997, entitled "SCANNING ELECTRON MICROSCOPE SYSTEM AND METHOD OF MANUFACTURING AN INTEGRATED CIRCUIT," the disclosure which is hereby incorporated by reference in its entirety, a wafer is analyzed and includes the step of scanning the wafer to produce a scanned waveform signal, which is then processed and compared to a reference signal to access the wafer. The scanned waveform signal is processed using an auto-correlation operation to produce a processed signal, which is compared to a reference signal. However, in that application, there is no weighting of the various parts to emphasize or diagnose signal deviations to allow the physical relationship between the signal parts and the physical object to be separated. Thus, it is possible to confound any scale of patterned features.